Overheating in hot weather can cause an unusually high body temperature. In most cases, however, fevers are an immune reaction.
A raised temperature assists the immune system as it attempts to fight off infection from viruses, bacteria, and some other pathogens.
Fevers can be scary, especially in young children, who tend to spike very high temperatures. Parents often worry about any body temperature higher than 98.6°F.
Because body temperature can vary by a degree or two, most doctors define a fever as a temperature that exceeds 99.5ºF when measured orally. Armpit temperatures indicate a fever at 99ºF or higher. Rectal temperatures are about a degree warmer than oral temperatures, so a rectal fever begins at about 100.4°F.
Fevers themselves do not cause the damage; it is the underlying disease that causes the biggest problem. Myths about brain injuries due to fevers have convinced many people that all fevers need treatment but that is not the case.
In people that do not have any health issues, fevers do not necessarily need to be treated. In fact, treating a fever to enable a person to get back to their usual activities is unwise. Doing so can slow the body’s ability to fight the infection.
Some research suggests that the fevers that often develop after a child has been given a vaccination actually support immunity. The report continues that fevers don’t mean that a child is sick, so a doctor should be consulted before any treatment for the fever is given.
If a fever is causing discomfort in the form of chills or muscle aches, people should consider home treatment. Children who have a fever but who seem happy and continue playing probably don’t need treatment.
Over-the-counter fever medications, such as ibuprofen, aspirin, and acetaminophen can lower fevers. Caregivers should consult a doctor before using any over-the-counter drug on a child under the age of two. These medications can produce serious side effects.
Aspirin should not be prescribed to children or teenagers to reduce a fever. Although rare in older teenagers, younger children can develop a life-threatening condition called Reye syndrome.
To avoid any possible side effects from over-the-counter drugs, there are a number of nonmedical options that can be taken to safely break a fever. These options include:
- Avoiding wearing too many layers, even when cold.
- Drinking plenty of cool, clear fluids. Water and electrolyte drinks are particularly helpful. Caregivers should avoid giving children large quantities of sweetened drinks, including juice.
- Trying cool compresses on the head.
- Resting and avoiding going to work or school. People are probably contagious if they have a fever. Pushing too hard can slow recovery time and make people feel worse. They should not take drugs so that they can go about their usual activities.
Fevers may be scary, but they help the immune system mount a strong defense. People should treat their fever as a sign that they need to take it easy for a few days. Doing so helps them quickly feel better.
People should call a doctor about a fever if:
- It rises above 105°F
- The fever lasts longer than 3 days, or remains high in spite of home treatment
- The fever is accompanied by a rash
- The fever is associated with intense pain or swelling in any area of the body, which suggests an infection
People should seek emergency medical care for a fever if:
- A child experiences a seizure for the first time, or a seizure that lasts longer than 5 minutes
- The person or their child has a weakened immune system
- The fever is accompanied by confusion or loss of consciousness
- The fever is accompanied by a rapidly spreading rash or a wound with streaks, which suggests a serious tissue infection
- The fever is accompanied by signs of dehydration, such as very dark urine or urinating less than three times a day
- The child is under 3 months old
Fevers in young babies and other vulnerable populations
Babies under 3 months old have underdeveloped immune systems. They are also poorly equipped to manage a fever. If a baby is younger than 3 months old, they should not receive fever-lowering medication. Caregivers should call a doctor or go to the emergency room, since a fever can signal a dangerous infection.
Some babies and young children experience seizures during a fever. Although they are frightening, febrile seizures typically cause brain damage only when they exceed 30 minutes in length.
Typical fever management strategies can help children feel better, but they won’t prevent febrile seizures. Instead, caregivers should keep the child as safe as possible during the seizure by:
- Placing the child on their side on a flat, protected surface to minimize the risk of injury
- Monitoring the child to ensure they do not choke
- Timing the seizure and contacting emergency services if the seizure exceeds 5 minutes
If a child experiences a febrile seizure, they should see a pediatrician. A doctor may recommend treatment with phenobarbitol or a similar drug if the child lives in a remote region where emergency services are inaccessible, or if the child has a history of very long seizures.
Some other groups also need immediate medical attention for a fever. Prompt care is needed if:
Fevers occur with a wide range of symptoms and ailments. Most doctors consider symptoms when working out how serious a fever is.
Some of the most common causes of fevers include:
- Sinus infections
- The common cold
- Localized infections, such as in the skin, urinary tract, ears, or gums
- Influenza (the flu)
- Immune reactions to childhood vaccinations
- Gastrointestinal infections
Less frequently, a fever can signal a chronic illness or life-threatening condition such as meningitis. Autoimmune conditions, such as arthritis, colitis, and lupus sometimes cause fevers.
A person that has an unexplained fever that persists for several weeks must talk to a doctor as it may indicate cancers, such as leukemia, Hodgkin’s disease, and non-Hodgkin’s lymphoma.
A blood clot deep in the veins can cause a fever, but is usually accompanied by symptoms, such as localized pain, redness, and swelling.